The present invention relates to a process for preparing polytetramethylene adipamide (nylon-4,6) by making a polymer based on adipic acid and 1,4-diaminobutane which polymer may be converted by further condensation, if desired or necessary, into a high-molecular weight polyamide.
A prepolymer can be made in a liquid phase by heating the salt of adipic acid and 1,4-diaminobutane at an elevated pressure until a prepolymer is formed and then a higher molecular weight polyamide can be obtained by allowing the prepolymer to condense further in solid form. Disadvantageously in such process the reactions necessarily take place in an autoclave. Such process employs high pressures and temperatures. As a consequence of such processing conditions, a substantial capital investment in plant and equipment.
It is also known in the art to react diaminobutane and adipic acid chloride in a boundary surface polymerization process. Such processes are described in, for instance, 50 J. Polymer Sci. 87 (1961) and Bull. Soc. Chem. 553 (France 1970). A chief drawback to such a process is the formation of hydrochloric acid.
An object of the present invention is to make a polytetramethylene adipamide polymer is a simple manner without the abovedescribed drawbacks. This and other objects of the present invention will become readily apparent from the following description of the invention.